In these years, portable terminal devices such as a cellular phone, a portable information terminal device, for example, have been widely used. In accordance with the development of communication networks and the more advanced functions of a terminal device itself, also has been used is a portable animation reproducing terminal capable of exchanging information intuitively and efficiently by reproducing video images and animation.
Here, as an animation reproducing method, Japanese Unexamined Patent Publication No. 275244/1998 (Tokukaihei 10-275244; published on Oct. 13, 1998) discloses a method to display animation by transmitting key frames and interpolating the key frames. Further, Japanese Unexamined Patent Publication No. 225168/1999 (Tokukaihei 11-225168; published on Aug. 17, 1999) discloses a method to dynamically change video and audio reproducing quality by sending and receiving information regarding a transmission method/transmission format in addition to transmission data when transmitting bit stream indicating moving images.
However, due to the need for portability, the throughput such as function/performance of a portable animation reproducing terminal is set lower compared with a general-purpose desktop computer, thereby causing that there inevitably exist various device types having various throughput. As a result, when different animation data require a variety of throughputs for reproduction, one animation reproducing terminal may be able to reproduce animation data, but another animation reproducing terminal may not be able to reproduce the animation data at a sufficient speed or may not be able to reproduce all of the animation data. Consequently, when such an animation reproducing terminal directly reproduces animation data, there is a problem that the intention of the creator may not be correctly conveyed.
In other words, a portable animation reproducing terminal is ideally desired to have (a) advanced functions such as high resolution display and multiple tone gradation color display, (b) high computing power, (c) capability of plotting graphics and characters at high speed, and (d) compact and light-weight with a long operating time. However, unlike a desktop computer, because of the need for portability, the portable animation reproducing terminal is difficult to satisfy all of those requirements of function, performance, dimensions, weight, and operating time. Accordingly, there are a wide variety of device types each having functions in accordance with its use. For example, for use whose main concern is the reduction of dimensions and weight, the device has limited functions.
As a result, when animation data is created and delivered in conformity to an animation reproducing terminal having advanced functions, it is likely that some animation reproducing terminals cannot reproduce the animation data at a sufficient speed due to an insufficient plotting and computing speed, for example, or cannot reproduce part of the animation data due to lack of function such as sound output, for example. Consequently, failure in outputting sound, frame missing, etc. may prevent the intensions of the creator from being correctly conveyed. On the other hand, when animation data is created in conformity to a low-function terminal and delivered, its expressiveness becomes poor.
Further, Japanese Unexamined Patent Publication No. 296157/1999 (Tokukaihei 11-296157; published on Oct. 29, 1999) discloses a technique to ensure real time animation by not performing plotting of the graphics that was not plotted within an allotted time to reproduce one scene, when displaying animation. Further, the Publication also discloses a technique to display by priority the graphics whose plotting is indispensable, in such a manner that the graphics that were not plotted in a scene whose plotting was interrupted are plotted by priority in its subsequent scene or that different graphics are given different priority of plotting in each scene.
However, with the technique disclosed in the Publication, the animation displayed by interrupting plotting differs from the original content of the animation. Further, the technique assumes a case where a frame rate is high. Thus, the effects are small in a case where a frame rate is low and a frame rate varies in response to the throughput of a reproducing device as in the animation method described in Tokukaihei 10-275244.
In view of the foregoing problems, the present invention has an objective to provide an animation reproducing terminal, a method for reproducing animation, and a program for realizing the animation reproducing terminal causing that, even when animation reproducing terminals having a variety of throughputs reproduce animation data having various complexities, (A) an animation reproducing terminal having sufficient throughput directly reproduces the animation data, while (B) an animation reproducing terminal having insufficient throughput can prevent defects that animation in which data of some types are missing and animation having many missing frames are reproduced.